Emerging research in cardiac resynchronisation therapy in the systemic right ventricle: one pace at a time

The systemic right ventricle (SRV) represents a range of congenital lesions; including complete transposition of the great arteries (TGA) with previous atrial switch repair, congenitally corrected transposition of the great arteries (ccTGA) and the more complex lesions- double inlet right ventricle and hypoplastic left heart syndrome palliated with Fontan and Norwood-Fontan respectively. 

The right ventricle has embryological, anatomical and electrophysiological differences that make it unsuitable for the burden of the systemic circulation compared to the left ventricle. As a consequence, the SRV can fail leading to congestive cardiac failure (CCF), the most common cause of mortality in the adult congenital heart disease (ACHD) population.

The main stay of treatment in this cohort is pharmacological; however cardiac resynchronisation therapy (CRT), ventricular assist devices and transplantation can also play a role. Kharbanda et al aim to identify predictors of outcome in ACHD patients with a SRV requiring CRT¹.

The authors carried out a retrospective multicentre study which included 13 centres in the United States, Canada and Europe; with a total of 80 patients with TGA and previous atrial switch repair and ccTGA. Data were collected on short and long-term outcomes with regards to pre- and post-CRT New York Heart Association (NYHA) functional class, systemic ventricular ejection fraction and QRS duration as well as hospital readmission due to CCF and mortality.

Interesting findings included:

• During short (< 6months) and long (>6months) term follow up; there was a significant improvement in NYHA functional class and a reduction in QRS duration in patients with ventricular pacing prior to CRT (i.e. CRT upgrade).
• These improvements were not mirrored in patients with a de novo implant. In fact during long term follow up there was a significant increase in the QRS duration and no improvement in NYHA functional class in the de novo group.
• During short term follow up there was no improvement in ejection fraction in both groups and only a minimal improvement in the CRT upgrade group on long term follow up ( 31% vs. 30%, p=0.049)
• Just over a quarter of the study cohort (26%) were readmitted due to CCF; and the presence of hypertension or diabetes at baseline was significantly associated with heart failure hospitalisation.

Previous studies have demonstrated that mortality and HF admissions after CRT in patients with ACHD were similar to that in non-ACHD patients² as well as that patients with a SRV responded better to CRT than those with a systemic left ventricle³. Kharbanda et al have added to an area of research where data are lacking and can at times be conflicting and where patient numbers are small, highlighting the need for a more evidence to support our approach to caring for patients with a SRV and ACHD as a whole.